BIOL 1202 Chapter : Ch 28 Protists
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NOTES FOR BIOLOGY 1202
DR. STEVEN POMARICO, INSTRUCTON
CHAPTER 28
Protists
• The Protists represents an unusual mix of organisms.
o Protists are more diverse than all other eukaryotes
o no longer considered a single kingdom
• The organisms found in this are all eukaryotes and most are single-celled for most of their life-cycle however but
some are colonial and there may even be multicellular forms.
• Remember the eukaryotic differences:
• Nucleus (with a double membrane)
• Organelles
• 2 or more chromosomes (DNA + proteins)
• Since the Protista are eukaryotic cells, they are clearly different from the Bacteria and Archaea.
o The differences between the protists and the rest of the eukaryotes are not quite as clear.
• Protists are nutritionally diverse and can be organized them into general groups based on nutritional methods:
• Autotrophic (photosynthetic)
• Heterotrophic (decomposers)
• Heterotrophic (ingestion - hunters and symbiotic)
• Mixotrophic (combining photosynthesis and ingestive or absorptive methods)
o they can be divided into this, but its not really clear cut because they are all mixed up
o this may have happened with lateral gene transfer
o defining by molecular characteristics is very hard
ENDOSYMBIOSIS→ leads to hodgepodge characteristic
• The evolution of protists is the results of endosymbiosis (see fig. 28.2)
• Primary endosymbiosis resulted in plastid-bearing lineages, which evolved into red and green algae.
o one that got us chloroplasts and mitochondria
▪ post ingestion of chloroplast led to a loss of one of the membranes
o ingestion of prokaryotic cell
o
• Secondary endosymbiosis resulted in greater diversification.
o ingestion of a eukaryotic cell into a eukaryotic cell
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o
o end up with more genetic material to work with and more chromosomes and such
o engulfing may have occurred more than once and may have had multiple different eukaryotic
cells engulfing eukaryotic cells
o you would expect molecular data to be similar if they engulfed green algea long ago
o makes it much more difficult to tease out relationships
▪ who is related based on shared ancestry vs secondary endosymbiosis
SUPERGROUPS
• The current state of what was kingdom protista is five supergroups (not kingdoms because we aren’t ready to call
them that yet)
•
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• Excavates
• Chromalveolates
• Rhizarians
• Archaeplastids
o problem: contains the plant kingdom
o take plant kingdom and fold it into the protists or take those protists and fold them into the plant
kingdom
▪ data here is also strong
• Unikontes
o Problem: contains the fungi and animals kingdoms
o may end up splitting unikotes into 2 separate groups and then splitting those kingdoms into two
saying those protists are anscestors of fungal or animal kingdom
▪ the data here is pretty strong
Excavates
• move via flagella
o flagella are back and forth motion not whirling propeller, also mechanism that does this is different
too
• have a feeding groove
• heterotrophic and have modified mitochondria→look very different from the normal eukaryotic, but we
don’t know if this creates a functional difference
• The two largest clades of the excavates are the diplomonads and the parabasalids (appear to be
sister taxa, more related than eugenozoans
• Diplomonads
o both free living and symbiotic species (means single cells)
▪ most symbiotic relationships is comencalist: protsists nor animal benefit or they are
parasitic where protist gets benefits and victim gets downside
o have two nuclei
▪ ties us into memory device for name
o multiple flagella
o Giardia (see fig 28.3) is a member of this group – infection results from drinks untreated water
causing diarrhea etc.
▪ found on every continent other than the artic
▪ parasite is not directly attacking your body, but is eating prokaryotes that are in your body
▪ can get even in incredibly clean water
o often most of the time this group causes discomfort or infection due to them getting in intestines,
some do get into blood stream though
• Parabasalids
o anaerobic→defining trait
▪ reason for this: they live in large intestines, struggles more when oxygen is present
o all known species are symbiotic and some are parasitic
▪ large number are parasitic some are commensalitic
o Trichomanas vaginalis (see fig 28.4) is a sexually transmitted member of this group – males
can often be asymptomatic.
▪ can inhabit vagina, uterus, and penis—eats cells that are part of lining of these
▪ symptoms: male—not a lot of signs, not a lot of bacteria here so doesn’t effect them,
female—when parasite does eating it allows for opportunistic area for bacterial infections
to do damage
▪ one of the most common and least reported sexually transmitted disease
• Euglenozoans is a diverse clade in the excavate linage.(zoan-means animal or animal like behavior)
o have distinctive mitochondria
o move via flagella—way it is structured separates it from all other eukaryotic flagella
o mixed nutritional methods (i.e mixotrophic)
o There are two major groups of euglenozoans, the euglenids and the kinetoplastids
▪ Euglenids
• Most are freshwater
• free living organisms, not in any symbiotic relationship
Document Summary
Endosymbiosis leads to hodgepodge characteristic: the evolution of protists is the results of endosymbiosis (see fig. Supergroups: the current state of what was kingdom protista is five supergroups (not kingdoms because we aren"t ready to call them that yet, excavates, chromalveolates, rhizarians, archaeplastids. 28. 7: kinetoplastids, one flagellum, single large mitochondrion, both free living and symbiotic species, some of the symbiotic species are parasitic. 6 these look like plants but they aren"t, tidal plant. 8: apicoplexans (a. k. a sporozoans, all are hetrotrophic (ingestion and absorption) and most are parasites which have a mobile stage called a. **external multichambered shell known as tests composed of caco3: made of calcium carbonate abundant material in most aquatic system, how seashells are made individual species have individual shell patterns. Many species characterized based on shell morphology. leave exceptionally good fossils. Pseudopodia extend through pores in the shell very important to food web in fish in la.
